Explosive cartridge having coupling and centering means



S. F. FOSTER Oct. 4, 1966 EXPLOSIVE CARTRIDGE HAVING COUPLING AND CENTERING MEANS Filed April 6, 1965 INVENTOR.

AGENT STEPHEN F FOSTER BY My PM fol United States Patent 3,276,370 EXPLUSIVE CARTRIDGE HAVING COUPLING AND CENTERING MEANS Stephen F. Foster, Hopatcong, N.J., assignor to Hercules Incorporated, a corporation of Delaware Filed Apr. 6, 1965, Ser. No. 445,914 Claims. (Cl. 102-24) This invention relates to explosive cartridges and more particularly to explosive cartridges which are designed to be frictionally coupled with like explosive cartridges and to center the cartridges in a borehole for purposes of smooth contour blasting.

One object of the present invention is to provide an explosive cartridge for the aforesaid service which is positive in its action of connecting small diameter explosive charges in end-to-end abutting relationship and which serves also to center the charges in larger diameter boreholes.

Other objects of the invention are to provide an explosive cartridge adapted to be coupled with like cartridges wherein the cartridge is simple in construction, economical to manufacture and uniformly reliable.

In accordance with the present invention, there is provided an explosive cartridge which is designed to be frictionally coupled with like explosive cartridges and to center the cartridges in a borehole, the explosive cartridge comprising in combination a tubular body member having a plurality of equispaced radial fins extending equidistant from the body member throughout its length, a tubular male coupling of considerably less length than the body member having an open end portion extending into said body member at one end thereof and secured therein and having a closed end portion extending from said body member adapted to extend into and frictionally engage the body member of a like cartridge, an explosive charge extending from the closed end of the male coupling substantially throughout the length of the body member, and a seal for the explosive charge spaced from the other end of the body member a distance to accommodate in substantial abutment the closed end of the male coupling of a like container.

For a more complete understanding of the present invention and for further objects and advantages thereof, reference is now made to the accompanying drawing wherein reference symbols refer to like parts wherever they occur.

FIGURE 1 is a part sectional, part elevational view of an explosive cartridge in accordance with the present invention also showing, out of function, a fragmentary portion of a like container coupled therewith;

FIGURE 2 is a sectional view of the cartridge taken along line 2-2 of FIGURE 1; and

FIGURE 3 is an elevational view showing a series of the explosive cartridges coupled together and in place in a borehole.

Referring now to the drawing, there is illustrated an explosive cartridge having a tubular body member 11 with three equally spaced radial fins 12 extending from the 'body member. The fins 12 extend equidistant from the body member 11 and are of the same length as the body member. A tubular male coupling 13 of considerably less length than the body member 11 has an open end 14 at one end thereof and a closed end 15 at the other end. A restraining collar 16 formed as an integral part of the male coupling 13 is positioned about midway the length of the male coupling. Three saw-tooth peripheral beads represented by 17 and two saw-tooth peripheral beads represented by 18 were formed as an integral part of the male coupling 13 on the open end portion and on the closed end portion, respectively, of the male coupling. The beads have the apex of their saw-tooth configuration facing the collar 16 on each end portion of the male coupling 13 to insure that frictional biting engagement is attained to resist any tendency in respect to separation of an assembly of like cartridges due to tensile force.

An explosive charge 19 was placed within the cartridge 10 and a seal 20 for the explosive charge was placed thereover. The seal 20 and charge length are spaced so that the end of the tubular body member 11 fully accommodates the closed end of the male coupling of a like container in substantial abutment. It will be seen, therefore, that the explosive charge is of small diameter within the cartridge spider or fins and that it extends from the closed end 15 of the male coupling 13 substantially throughout the cartridge to the seal 20.

In making up an explosive column in accordance with the invention, a first explosive cartridge and a second explosive cartridge simply have the male coupling of one pushed into the body member of the other. This procedure is repeated by addition until an assembly of the desired number of cartridges is obtained. The cartridges may be completely assembled outside the borehole and pushed therein or may be incrementally pushed therein as additional units are added. In either event, the assembled column of cartridges is centered in the borehole with the explosive charges in end-to-end abutting relationship as shown in FIGURE 3.

An important feature of the invention resides in having the explosive charges within the explosive cartridges in substantially contiguous relationship throughout a column assembly of the cartridges. To insure this, although a tight slip fit interconnection between the cartridges may be used, it is quite preferable to have the tubular male coupling provided with frictional engaging means. Such means include the saw-tooth peripheral beads as heretofore described as well as discontinuous beads or a plurality of individual projections spaced along the male coupling and the like. All such means in a preferable embodiment of the invention should preferably have a sharp apex for increasing the frictional resistance by biting-like engagement. Such engagement compensates for tolerance variations and in addition, permits a simple force fit in making up the cartridges in the factory and permits a simple force fit in making up the cartridge assemblies in the field.

From the foregoing, it will be appreciated that no useful purpose is served in having more than three fins, although more than three may be utilized, since such surplusage detracts from the economy of the cartridge. Accordingly, as an example of a commercially sized preferred embodiment of the invention, the tubular body member depicted in FIGURE 1 was formed by extruding high-density polyethylene characterized by a melt index of 0.6 to 0.8 (L at C.) and then cutting the extruded piece into lengths about 22 inches long. The inside diameter of the body member was 0.63 inch (1.005) with a 30 mils wall thickness, and the outside diameter of the fins was 1% inches with a 30 mils thickness for the fins.

The tubular male coupling was formed by blow molding the same type polyethylene in a 6.0 inches long mold and then cutting the blown piece in half to give two 3.0 inches long male couplings, each section having an open end and a closed end with peripheral beads thereon and a collar therebetween. The collar was spaced about 1 inches from the open end, was 4; inch wide and had a diameter of inch. The three peripheral beads for the open end portion were spaced beginning about /z inch from the open end, were inch wide and were spaced 7 inch therebetween. The two peripheral beads for the closed end portion were spaced beginning inch from the closed end and had the same width and spacing as the other beads. The diameter of both end portions of the male coupling at the collar was 0.63 inch and at the ends thereof 0.615 inch, thus giving a slight taper. The apex of all beads faced the collar and extended 0.005 inch above the body portions. The wall thickness of the tubular male coupling was 30 mils, and the fiat end closure at its periphery had a A inch radius. The open end portion of the male coupling was force inserted into the tubular body member up to the collar and the length of the overall device from the end of the body member to the closed end of the male coupling was 24 inches.

The device as described above was filled with a conventional blasting explosive to within about 1 /2 inches of the end of the tubular body member thereby leaving space for accommodation of the male coupling of a like device. This gave an explosive charge length of about 22 /2 inches, and a thin force fitted plastic seal was placed thereover to complete manufacture of the cartridge. T-he cartridges thus manufactured were tested as assemblies thereof and were found to give exceptional results for smooth contour blasting and particularly for the arch section of rock formations where blasting is carried out in horizontal planes and where heretofore, radial fracture damage to the rock was a common occurrence. Moreover, it will be found that the cartridges in accordance with the present invention have special utility under conditions where'water is encountered in storage or in blasting.

Furthermore, it will be appreciated that although highdensity polyethylene is preferred for the tubular body members and for the tubular male coupling, other thermoplastic materials may be used such as polyolefins generally, and copolymers and alloys thereof and other materials such as plasticized po1y(vinyl chloride), rigid poly (vinyl chloride), plast-icized vinyl chloride-vinyl acetate copolymer, ABS terpolymer and the like. Similarly, any of the aforementioned plastics may be used as the force fitted plastic seal although other types of seals may be used including sealing compounds and the like placed over the explosive. Ordinarily, explosive charge diameters for smooth contour blasting will not exceed about one inch, and the coupling device and size of borehole will be proportionately increased to accommodate any such other sizes.

It will be seen, therefore, that this invention may be carried out by the use of various modifications and changes without departing from its spirit and scope, with only such limitations placed thereon as are imposed by the appended claims.

What I claim and desire to protect by Letters Patent is:

1. An explosive cartridge which is designed to be frictionally coupled with like explosive cartridges and to center the cartridges in a borehole, the explosive cartridge comprising in combination:

(a) a tubular body member having a plurality of equispaced radial fins extending equidistant from the body member throughout its length,

(b) a tubular male coupling of considerably less length than the body member having an open end portion extending into said body member at one end thereof and secured therein and having a closed end portion extending from said body member adapted to extend into and frictionally engage the body member of a like cartridge,

(c) an explosive charge extending from the closed end of the male coupling substantially throughout the length of the body member, and

(d) a seal for the explosive charge spaced from the other end of the body member a distance to accommodate in substantial abutment the closed end of the male coupling of a like container.

2. An explosive cartridge which is designed to be frictionally coupled with like explosive cartridges and to center the cartridges in a borehole, the explosive cartridge comprising in combination:

(a) three equispaced radial fins extending equidistant from the body member throughout its length,

(b) a tubular male coupling of considerably less length than the body member having an open end portion extending into said body member at one end thereof and having a closed end portion extending from said body member, said end portions being divided by a restraining collar and having frictional engaging means thereon to frictionally secure the open end portion within the body member up to the collar and to frictionally engage up to the collar the closed end portion within the body member of a like cartridge,

(c) an explosive charge extending from the closed end of the male coupling substantially throughout the length of the body member, and

(d) a seal for the explosive charge spaced from the other end of the body member a distance to accommodate in substantial abutment the closed end of the male coupling of a like container.

3. The explosive cartridge according to claim 2 wherein the frictional engaging means comprises a plurality of peripheral beads on the open end portion of the male coupling and a plurality of peripheral beads on the closed end portion of the male coupling.

4. The explosive cartridge according to claim 2 where in the frictional engaging means comprises three sawtooth peripheral beads on the open end portion of the male coupling and two saw-tooth peripheral beads on the closed end portion of the male coupling.

5. The explosive cartridge according to claim 2 wherein the tubular body member and the tubular male coupling are high-density polyethylene.

References Cited by the Examiner UNITED STATES PATENTS 710,323 9/1902 Hatfield 10221.8 721,432 2/1903 Durham 10224 2,377,151 5/ 1945 Huber 10224 2,525,703 10/ 1950 McGirr 102-24 2,755,735 6/ 1956 Harter 102-24 BENJAMIN A. BORCHELT, Primary Examiner. V. R. PENDEGRASS, Assistant Examiner. 

1. AN EXPLOSIVE CARTRIDGE WHICH IS DESIGNED TO BE FRICTIONALLY COUPLED WITH LIKE EXPLOSIVE CARTRIDGES AND TO CENTER THE CARTRIDGES IN A BOREHOLE, THE EXPLOSIVE CARTRIDGE COMPRISING IN COMBINATION: (A) A TUBULAR BODY MEMBER HAVING A PLURALITY OF EQUISPACED RADIAL FINS EXTENDING EQUIDISTANT FROM THE BODY MEMBER THROUGHOUT ITS LENGTH, (B) A TUBULAR MALE COUPLING OF CONSIDERABLY LESS LENGTH THAN THE BODY MEMBER HAVING AN OPEN END PORTION EXTENDING INTO SAID BODY MEMBER AT ONE END THEREOF AND SECURED THEREIN AND HAVING A CLOSED END PORTION EXTENDING FROM SAID BODY MEMBER ADAPTED TO EXTEND INTO AND FRICTIONALLY ENGAGE THE BODY MEMBER OF A LIKE CARTRIDGE, (C) AN EXPLOSIVE CHARGE EXTENDING FROM THE CLOSED END OF THE MALE COUPLING SUBSTANTIALLY THROUGHOUT THE LENGTH OF THE BODY MEMBER, AND (D) A SEAL FOR THE EXPLOSIVE CHARGE SPACED FROM THE OTHER END OF THE BODY MEMBER A DISTANCE TO ACCOMMODATE IN SUBSTANTIAL ABUTMENT THE CLOSED END OF THE MALE COUPLING OF A LIKE CONTAINER. 